This invention relates generally to the art of non-impact ink jet printing, and more particularly to ink supply systems for ink jet print heads.
An asynchronous volume displacement droplet ejection type of ink jet head is described in U.S. Pat. No. 3,946,398--Kyser et al (1976) and co-pending patent application Ser. No. 489,985, filed July 19, 1974, both assigned to the assignee of the present application. A piezoelectric element is associated with an ink jet chamber, resulting in ejecting a droplet of ink from a nozzle of the chamber with sufficient velocity for it to travel to a recording medium. One such droplet forms a portion of a character to be printed. A plurality, such as seven of nine, print heads of this type are preferably built as a single structure that is mechanically swept across a recording medium upon which the printing is taking place line by line. At each column of the printing line the appropriate number of the independently controllable ink jet chambers are fired by pulsing their respective piezoelectric elements to eject ink drops therefrom.
Such ink jet heads require, of course, a supply of ink to their chambers to replace the ink that is ejected as droplets. An ink supply system for the asynchronous type of ink jet head which utilizes a pre-filled insertable ink cartridge is described in co-pending patent application Ser. No. 807,219, filed June 16, 1977, a division of co-pending application Ser. No. 694,064, filed June 7, 1976, both of which are assigned now U.S. Pat. No. 4,074,284, issued Feb. 14, 1978, to the same assignee as the present application. The goal of prior ink supply design efforts have been to deliver ink under constant pressure and free of bubbles and impurities. Other efforts have been directed toward making ink containers refillable or interchangeable. However, much of this prior work is not entirely effective for many particular applications.
It is an objective of the present invention to provide an improved technique for supplying ink to an ink jet printer under constant pressure over time that is above atmospheric pressure.
It is another objective of the present invention to deliver ink free from contamination by bubbles and impurities.
It is a further objective of the present invention to supply ink in a manner that the ink container can readily be removed and replaced by another container.